Graphene Oxide Hydroxyapatite Research Articles

Tuning of Graphene oxide - Hydroxyapatite (GO-HAp) composite for enhanced fluorescence and anti-oxidant properties-green approach

Many researchers are working on doping and co-doping of HAp with metal ions and rare earth elements to improve the applicability of HAp, but all these studies question the biocompatibility of HAp. Further, there are no reports on the fluorescence and anti-oxidant aspects. Graphene oxide being a non-toxic material, with excellent physiochemical properties can enhance and induce new properties in HAp. The present study explored the transformation of sea wastes into valuable products such as HAp reduces the negative impact on the environment. GO (from cellulose) and HAp (from Anadara granosa, Crassostrea virginica, synthetic CaCO3). The prepared composite material from two different methods (Post-modification and In situ) of three different precursors are compared and contrasted. From the PXRD results, P-GO-HAp has retained both GO and HAp phases with high crystallinity. The hydrophilicity and higher calcium ratio in P-GO-HApS, the presence of β – TCP phase after composite formation in P-GO-HApC & P-GO-HApO has improved its utility in bone implants. Also, the intense bluish-green emission of P-GO-HApC & P-GO-HApO paves the way for biocompatible imaging. The interplay of calcium, improved hydrophilicity, and stable radical sites of the conjugated π system of GO paved the way for antioxidant property in P-GO-HApS with a radical scavenging potential of 32.88%. With the increase in antioxidant properties, the composite has enhanced inhibition on the most common dental infection caused by Streptococcus mutans.

Synthesis and characterization of hydroxyapatite self-assembled nanocomposites on graphene oxide sheets from seashell waste: A green process for regenerative medicine

Bone transplantation is the second most common transplantation surgery in the world. Therefore, there is an urgent need for artificial bone transplantation to repair bone defects. In bone tissue engineering, hydroxyapatite (HA) plays a major role in bone graft applications. This study deals with a facile method for synthesizing HA hexagonal nanorods from seashells by a solid-state hydrothermal transition process. The synthesized HA nanorods (∼2.29 nm) were reinforced with carbon nanotube and chitosan on graphene oxide sheets with polymeric support by in-situ synthetic approach. Among the synthesized nanocomposites viz., hydroxyapatite-graphene oxide (HA-GO), hydroxyapatite-graphene oxide-chitosan (HA-GO-CS), hydroxyapatite-graphene oxide-chitosan-carbon nanotube-polylactic acid (HA-GO–CS–CNT-PLA). Among them, the HA-GO–CS–CNT-PLA composite exhibits micro and macro porosity (∼200 to 600 μm), higher mechanical strength, (Hardness ∼90.5 ± 1.33 MPa; Tensile strength 25.62 MPa), and maximum cell viability in MG63 osteoblast-like cells (80%). The self-assembled hybrid-nanocomposite of HA-GO–CS–CNT-PLA is a promising material for bone filler application and could efficiently utilize seashell waste through the green process.

In situ synthesis and cell line studies of nano-hydroxyapatite/graphene oxide composite materials for bone support applications

The current work presents and discusses the findings of on the structural, chemical and thermal properties of in situ synthesis of graphene oxide-hydroxyapatite (GO/HA) nanocomposite materials doped with graphene oxide (w/w) at different ratios of 0%, 0.1%, 0.5% and 1% for bone tissue support applications. Microstructure and crystallinity were investigated by Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), pore structures by Brunauner-Emmett-Teller (BET) analysis, Dynamic light scattering (DLS). Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were performed to characterize the morphology of the bone support scaffold materials. The attachment and cell viability of fibroblast NIH/3T3 cells were observed on the synthesized bone support composite materials. Excellent proliferation of bone support scaffolds containing 0.5% and 1% GO (w/w) was observed by fluorescence microscopy using 3,3′-Dihexyloxacarbocyanine iodide (Dio-6), 4′,6-diamidino-2-phenylindole (DAPI), MitoRed and Anti-Vinculin. The innovative materials revealed in this study demonstrated that GO and HA promoted cell proliferation and cell adhesion with their well-compatible properties and helped cell penetration and colonization by increasing the surface area of GO, making them promising materials for bone support applications.

ELECTRODEPOSITED GRAPHENE OXIDE-HYDROXYAPATITE COMPOSITE COATING WITH IMPROVED BONDING STRENGTH FOR BIOMEDICAL APPLICATION

In order to improve the interfacial bonding at coating-substrate, a graphene oxide-hydroxyapatite (GH) coating was designed and constructed. The microstructure, bonding strength and in vitro bioactivity of the coating were analyzed. The results showed that GH coating presented uniform and crack-free structure with a flake morphology. The bonding strength of GH coating was 7.81[Formula: see text]MPa, which is about 1.2 times that of pure hydroxyapatite coating. In vitro bioactivity test using simulated body fluid exhibited that GH coating processes the ability to induce apatite formation. The GH coating should have potential application in surface modification for biomedical materials.

Chitosan/Xanthan/Hydroxyapatite-graphene oxide porous scaffold associated with mesenchymal stem cells for dentin-pulp complex regeneration.

The aim of this paper was to synthesize and characterize polymeric scaffolds of Chitosan/Xanthan/Hydroxyapatite-Graphene Oxide nanocomposite associated with mesenchymal stem cells for regenerative dentistry application. The chitosan-xanthan gum (CX) complex was associated with Hydroxyapatite-Graphene Oxide (HA-GO) nanocomposite with different Graphene Oxides (GO) concentration (0.5 wt%; 1.0 wt%; 1.5 wt%). The scaffolds characterizations were performed by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Raman spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and contact angle. The mechanical properties were assessed by compressive strength. The in vitro bioactivity and the in vitro cytotoxicity test (MTT test) were analyzed as well. The data was submitted to the Normality and Homogeneity tests. In vitro Indirect Cytotoxicity assay data was statistically analyzed by ANOVA two-way, followed by Tukey's test (α = 0.05). Compressive strength and contact angle data were statistically analyzed by one-way ANOVA, followed by Tukey's test (α = 0.05). XRD showed the presence of Hydroxyapatite (HA) peaks in the structures CXHA, CXHAGO 0.5%,1.0% and 1.5%. FT-IR showed amino and carboxylic bands characteristic of CX. Raman spectroscopy analysis evidenced a high quality of the GO. In the TGA it was observed the mass loss associated with the CX degradation by depolymerization. SEM analysis showed pores in the scaffolds, in addition to HA incorporated and adhered to the polymer. Contact angle test showed that scaffolds have a hydrophilic characteristic, with the CX group the highest contact angle and CXHA the lowest (p < 0.05). 1.0 wt% GO significantly increased the compressive strength compared to other compositions. In the bioactivity test, the apatite crystals precipitation on the scaffold surface was observed. MTT test showed high cell viability in CXHAGO 1.0% and CXHAGO 1.5% scaffold. CXHAGO scaffolds are promising for regenerative dentistry application because they have morphological characteristics, mechanical and biological properties favorable for the regeneration process.

Green synthesis of graphene-hydroxyapatite nanocomposites with improved mechanical properties for bone implant materials

Herein, an in-situ synthesis of reduced graphene oxide-hydroxyapatite (RGO-HA) nanocomposites via a green reduction protocol is presented. 0.5, 1.0, and 1.5 wt% of RGO in HA are obtained by reducing the precursor solution with custard apple leaf extract. The 10x5 mm-sized discs of the RGO-HA nanocomposites are prepared and investigated for their mechanical properties. The presence of graphene in the composites is confirmed by UV–Visible, Raman spectroscopic techniques while XRD spectral analysis confirmed the α-tricalcium phosphate (TCP, JCPDS PDF No 00-009-0432) structure of HA. Nanoindentation and Vicker indentation studies revealed the enhancement in the mechanical properties of RGO-HA nanocomposites: elastic modulus, microhardness, and fracture toughness values are enhanced by 100%, 33.3%, and 64.5 %respectively for 1.5 wt% of graphene in HA matrix. The FE SEM analysis of the indentation cracks revealed that the wrapped and tucked graphene sheets in the HA matrix have hindered the propagation of the crack through pull-out, ridge growth, bridging, and deflection mechanisms. Nano scratch analysis revealed the enhanced surface roughness (120%) and coefficient of friction (102%) for 1.5 wt% composites than pure HA. The same composite showed 100% viability of HEK 293 cells at 12.5 μg/mL concentration and in vitro apatite mineralization when immersed for 7 days under SBF solution.

Enhanced corrosion resistance, antibacterial and biological properties of sol-gel derived Ti-rGO-HAp nanocomposites

In the present work, pure Hydroxyapatite (HAp), Titanium-Hydroxyapatite (Ti-HAp), reduced Graphene oxide-Hydroxyapatite (rGO-HAp), and Titanium-reduced Graphene Oxide-Hydroxyapatite (Ti-rGO-HAp) nanocomposites were successfully synthesized using sol-gel technique. They are fabricated as films on 316 L stainless steel plate. The impact of the incorporation of Ti and rGO on properties (structural, optical, morphological, corrosion, antibacterial, and biocompatibility) of the HAp nanopowders are investigated. The hexagonal structure of the nanocomposites was observed through XRD spectrographs. The average crystallite size of the synthesized nanocomposites varies from 37 to 51 nm. The crystallite size was reduced due to the incorporation of Ti ions on the HAp surface. The surface morphology and chemical compositions of as-prepared samples are investigated using a scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDX), respectively. The antimicrobial activity and biocompatibility observations of the pure HAp and Ti-rGO-HAp nanocomposites demonstrated that titanium-added HAp nanocomposites exhibit more toxic in opposition to all bacterial strains and have no toxicity against live tissues. The incorporation of Ti and rGO ions increase polarization resistance with a decrease in current density from 8.7 to 3.0 A, which is observed in the corrosion tests of the manufactured films in the stimulated body fluid (SBF). The corrosion resistance efficiency, zone inhibition layer and improved biocompatibility show that the novel (Ti–rGO-HAp) nanocomposites are the potential candidate for biomedical applications-.

Chitosan/Xanthan membrane containing hydroxyapatite/Graphene oxide nanocomposite for guided bone regeneration

ObjectiveTo develop a chitosan-xanthan (CX) membrane associated with Hydroxyapatite (HA) and different concentrations of graphene oxide (GO). MethodologyThe CX complex was associated with the hydroxyapatite-graphene oxide (HAGO) nanocomposite in different concentrations. The experimental groups were:1) CX; 2) Chitosan-Xanthan/Hydroxyapatite (CXHA); 3) Chitosan-Xanthan/Hydroxyapatite-Graphene Oxide 0.5% (CXHAGO 0.5%); 4) CXHAGO 1.0%; 5) CXHAGO 1.5%. The membranes characterizations were performed by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Raman spectroscopy, Scanning Electron Microscopy (SEM), Contact angle, Tensile Strength, in vitro Bioactivity and the in vitro Cell viability (MTT test). The data was submitted to the Normality and Homogeneity tests. In vitro Indirect Cytotoxicity assay data was statistically analyzed by two-way ANOVA and Tukey's test (α = 0.05). Tensile Strength and Contact Angle data were statistically analyzed by one-way ANOVA followed by Tukey's test (α = 0.05). ResultsXRD, FTIR and Raman spectroscopy confirmed the characteristic bands of the CX polymeric complex, the phosphate bands related to HA, and the presence of GO. SEM images demonstrated the non-porous and homogeneous surface of membranes. The contact angle test showed the hydrophilic characteristic of all membranes (p > 0.05). CX showed tensile strength significantly higher than other membranes. The apatite deposition was observed in all membranes after performing the bioactivity test. The cell viability of CXHAGO 1.0% and CXHAGO 1.5% was significantly higher than CX. ConclusionThe addition of HAGO reduced the mechanical strength of membranes, but improved its cell viability. It demonstrated the potential of CXHAGO membranes to be used in guided bone regeneration therapies.

Preparation and performance of hydroxyapatite-graphene oxide composite microspheres

Drug-loaded microspheres have been widely studied and applied in biomedical materials, but there are still some open problems such as low drug loading and sudden release. In order to solve such problems, hydroxyapatite-graphene oxide (HA-GO) composite microspheres were prepared by using hydroxyapatite (HA) and graphene oxide (GO). Firstly, spherical calcium carbonate-graphene oxide (CaCO₃-GO) composites were synthesized by hard template method. Then, spherical hollow HA-GO composite microspheres were successfully prepared by a method of hydrothermal-assisted ion exchange. The effect of different synthesis conditions on the prepared HA-GO composites was studied. Through a series of measurements, such as X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman infrared spectroscopy, field emission scanning electron microscope (FESEM), ultraviolet visible spectrophotometer (UV-VIS), etc., the prepared samples were analyzed and characterized. The drug-loading performance of the microspheres was tested by using curcumin as the drug-loading model, and the drug-loading performance was evaluated by two indicators of encapsulation efficiency and drug-loading capacity. At the same time, the cytotoxicity test of the microsphere sample materials was also performed. The research results show that the reactant concentration of the system and the hydrothermal reaction time greatly affect the forming effect of the composite microspheres. When the initial reactant concentration is 0.3 mol/L and the hydrothermal reaction time is 6 h, hollow HA-GO composite microspheres with good morphology can be prepared, with a particle size from 5.1 μm to 7.7 μm and a pore size of about 40 nm. At the same time, it was found that the spherical structure can improve the drug loading, the drug encapsulation efficiency was (20.90 ± 0.31)%, and the drug loading was (2.95 ± 0.19)%. This shows that HA-GO composite microspheres have good medical application value.

Highly Porous Hydroxyapatite/Graphene Oxide/Chitosan Beads as an Efficient Adsorbent for Dyes and Heavy Metal Ions Removal.

Dye and heavy metal contaminants are mainly aquatic pollutants. Although many materials and methods have been developed to remove these pollutants from water, effective and cheap materials and methods are still challenging. In this study, highly porous hydroxyapatite/graphene oxide/chitosan beads (HGC) were prepared by a facile one-step method and investigated as efficient adsorbents. The prepared beads showed a high porosity and low bulk density. SEM images indicated that the hydroxyapatite (HA) nanoparticles and graphene oxide (GO) nanosheets were well dispersed on the CTS matrix. FT-IR spectra confirmed good incorporation of the three components. The adsorption behavior of the obtained beads to methylene blue (MB) and copper ions was investigated, including the effect of the contact time, pH medium, dye/metal ion initial concentration, and recycle ability. The HGC beads showed rapid adsorption, high capacity, and easy separation and reused due to the porous characteristics of GO sheets and HA nanoparticles as well as the rich negative charges of the chitosan (CTS) matrix. The maximum sorption capacities of the HGC beads were 99.00 and 256.41 mg g−1 for MB and copper ions removal, respectively.

Electrophoretic deposition of graphene oxide reinforced hydroxyapatite on the tantalum substrate for bone implant applications: In vitro corrosion and bio-tribological behavior

Tantalum (Ta) is used in dental implantology due to its high biocompatibility and potential clinical applications. Ta has low bone regeneration and low abrasion resistance , which can lead to inflammatory reactions in biological environments. In the present study, the graphene oxide/hydroxyapatite (GO/HA) composite on the Ta substrate was coated using the electrophoretic deposition technique. The deposition process was conducted at a constant voltage of 30 V at two deposition times of 5 and 10 min. Confocal Raman spectroscopy , Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) confirmed GO in the GO/HA composite coating layer. The roughness of samples increased from 35 ± 3 nm for the GO/HA-coated Ta (at 10 min) to 120 ± 4 nm for the uncoated Ta. After coating Ta with the GO/HA at deposition time of 10 min, nanoindentation curve shifted to the left and maximum depth decreased due to an 18-fold increase in the hardness of coated sample in comparison to the uncoated Ta. The GO/HA composite coating improved the bio-tribological behavior, the resistance to plastic deformation , and fracture toughness of Ta substrate. The stiffness of GO/HA-coated Ta (at 10 min) was 8-fold higher than that of the uncoated Ta. Additionally, the friction coefficient of GO/HA-coated Ta (0.3) was lower than the uncoated Ta (0.43). The GO/HA-coated Ta (at 10 min) showed significantly higher corrosion current density (18.6 ± 1.2 vs 4.97 ± 0.23 μA/cm 2 ) compared to the uncoated Ta. The results of antibacterial activity test indicated that the presence of GO in the GO/HA coating decreased the viability of Escherichia coli and Staphylococcus aureus cells on the surface of Ta. Due to higher surface roughness and wettability of the GO/HA-coated Ta compared to the uncoated Ta, the proliferation and viability of MG-63 cells on the surface of GO/HA-coated Ta significantly increased. Our findings demonstrated that the GO/HA composite coating can enhance the lifetime of Ta based dental and orthopedic implants. • The GO/ HA composite coating was successfully prepared and deposited on the Ta surface during EPD process. • The GO/ HA-coated Ta showed the high corrosion protection and antibacterial activity compare to the uncoated Ta. • The GO/ HA coating improved the bio-tribological behavior, resistance to plastic deformation, and fracture toughness of Ta. • The GO/HA caused an increase in the hydrophilicity and roughness, which enhanced the proliferation of cells on Ta surface. • The GO/HA composite coating on the Ta surface could be a promising candidate for dental and orthopedic implants.

Ambient temperature sulfonated carbon fiber reinforced PEEK with hydroxyapatite and reduced graphene oxide hydroxyapatite composite coating.

30% carbon fiber reinforced polyetheretherketone (CFR-PEEK) has in recent times, become significant in the orthopedic industry because its elastic modulus can be engineered to match that of the human bone. But it is bioinert and does not integrate well with the immediate bone tissue environment. In this study, a combined surface modification technique involving ambient temperature sulfonation and surface coating of (hydroxyapatite (HA), 5%reduced graphene oxide hydroxyapatite(5%RGO/HA) and 10%reduced graphene oxide hydroxyapatite(10%RGO/HA) composites) on 30%CFR-PEEK was achieved with an appropriate temperature treatment at 345°C in nitrogen. The coatings adhered unto the surface of S30%CFR-PEEK with an improved hydrophilicity and bioactivity. With the sample S30%CFR-PEEK+HA, having the highest enhanced hydrophilicity from 112.5 ± 2.5° to 20 ± 2° and bioactivity. An improvement in hydrophilicity and bioactivity depicts a change in surface chemistry which will have a positive impact in the interaction of the materials surface with immediate bone environment for a successful application in the orthopedic industry.

Nanocomposite powders of hydroxyapatite-graphene oxide for biological applications

The repair of bone fractures is a clinical challenge for patients with impaired healing, such as osteoporosis. Currently, different strategies have been developed to design new biomaterials, enhancing their interactions with biological systems and conducting the cellular behavior in the desired direction to help fracture healing. In the present work, hydroxyapatite-graphene oxide (HA-GO) nanocomposites were produced and the morphological and physicochemical influences of the addition of 0.5 wt%, 1.0 wt% and 1.5 wt% of GO to HA were observed. FEG-SEM and TEM analyses of HA-GO nanocomposites showed HA nanoparticles adhered to the surface of the GO sheets, suggesting an effective method to form nanostructured graphene-based biomaterials. As confirmation, physicochemical analyses by Raman, FTIR and TGA demonstrated a strong affinity between HA and GO, according to the increase of concentration from 0.5 wt% to 1.5 wt% GO in the HA-GO nanocomposites. Also, in order to evaluate the HA-GO nanocomposites behavior under biological microenvironment, in vitro bioactivity and indirect cytotoxicity tests were performed. FEG-SEM analyses confirmed the positive results for the bioactivity properties of HA-GO nanocomposite and indirect cytotoxicity demonstrated that even with a decrease in the hDPSCs viability and proliferation, when increasing to 1.5 wt% of GO concentration, high level of cell viability was exhibited by HA-GO nanocomposites. These biological results suggested the 0.5 wt% HA-GO nanocomposite as a potential bioactive bone graft and a promising biomaterial for bone tissue regeneration, when compared to the pure HA.

Dual-Anchoring Intercalation Structure and Enhanced Bioactivity of Poly(vinyl alcohol)/Graphene Oxide–Hydroxyapatite Nanocomposite Hydrogels as Artificial Cartilage Replacement

Through the dual-anchoring effect, hydroxyapatite (HA) molecules were intercalated into graphene oxide (GO) layers to form a GO–PEG–HA hybrid, and PVA/GO–PEG–HA nanocomposite hydrogels were prepare...

Effect of Fine‐Grained AZ91D Coating with Graphene Oxide/Hydroxyapatite on Biocompatibility

AbstractA graphene oxide/hydroxyapatite(GO/HA) composite coating were prepared on the surface of fine‐grained AZ91D magnesium alloy. The morphologies and structures of the coatings were characterized by Scanning Electron Microscopy and X‐Ray Diffraction. The corrosion behaviors were studied by polarization curve measurement and alternating current impedance spectroscopy, respectively. Also, the changes of the Mg2+ concentration in rat plasma were detected. Besides, changes of muscle, liver, and kidney in rats and bone in rabbit were tested to prove whether it was toxic to the body after implantation. Results showed that GO/HA‐AZ91D had good corrosion resistance. Compared to AZ91D, the corrosion potential, the membrane capacitance and the transfer resistance increased, the current decreased, and the corrosion performance was greatly improved. There was no significant difference of magnesium concentration among different groups. The structural characterization showed that the surface compactness of the composite coating was better, and the composite coating could effectively improve the corrosion resistance of the magnesium alloy.

RETRACTED ARTICLE:3D printing of surface characterisation and finite element analysis improvement of PEEK-HAP-GO in bone implant

Research and development of polyetheretherketone (PEEK) composites with high thermal conductivities and ideal thermal stabilities have become one of the hot topics in composites. However, not all PEEK composites have the necessary characteristics adequate fracture toughness to resist forces and crack propagation , with an improved mechanical and structural properties. This research evaluates a novel computational surface characterisation and finite element analysis (FEA) of polyetheretherketone and hydroxyapatite graphene oxide (PEEK-HAP-GO) in the process of 3D printing to improve fracture toughness to resist forces and crack propagation . It also focuses on increasing the hydrophilicity, surface roughness, and coating osteoconductive of PEEK-HAP-GO for the bone implant. Compression and tensile tests were performed to investigate the mechanical properties of the PEEK-HAP-GO structure. The addition of calcium phosphate and the incorporation of porosity in PEEK-HAP-GO has been identified as an effective way to improve the osseointegration of bone-implant interfaces of PEEK-HAP-GO. The further analytical structure of the particle was performed, evaluating the surface luminance structure and the profile structure of composite material in 3D printing, analysing the profile curve of the nanostructure from the scanning electron microscope (SEM). The results of the uniaxial compression tests in new PEEK-HAP-GO biodegradable materials show good compressive strength suitable for loading applications. It shows melt-blending with bioactive nanoparticles can be used to produce bioactive nanocomposites like HAP-GO and is used to modify the surface structure of PEEK implants in order to make it more bioactive.

In situ syntheses of hydroxyapatite-grafted graphene oxide composites.

In this study, we examined three different syntheses of hydroxyapatite (HAp) and graphene oxide-hydroxyapatite (GO-HAp) composites with a GO content of 9, 33, and 43% wt. The materials were prepared from various precursors of calcium and phosphate ions, using an in situ synthesis method, with mild conditions to avoid reducing the GO. In situ bonding technology proposed that calcium ions bond with GO at first and then HAp nanoflakes in situ grow on GO sheets, forming GO-HAp nanocomposite. The aim of the present work was to analyze the differences due to the use of different starting reagents and verify, with the addition of increasing amounts of GO, the changes in morphology, crystallinity, and solubility of the obtained HAp composites. Detailed structural and morphological characterization studies of the composites were carried out using scanning electron microscopy, energy dispersive X-ray spectrometry, X-ray powder diffraction, Raman spectroscopy, and Fourier transform infrared spectroscopy. We found that GO sheets act as a nucleation site for HAp mineralization, but we observed a loss of the crystallographic order due to the intercalation of the graphenic sheets between the HAp particles.

Interactions between HA/GO/epoxy resin nanocomposites: optimization, modeling and mechanical performance using central composite design and genetic algorithm

This study is focused on the role of hydroxyapatite (HA) nanoparticles and graphene oxide (GO) nanoplates on the flexural and compression properties of epoxy-based hybrid nanocomposites. In the first step, epoxy-based hybrid nanocomposites were reinforced by different HA nanoparticles and GO nanoplates up to 7 wt% and 0.5 wt%, respectively. Filler’s weight fractions that used as design parameters have been achieved by central composite design method in Minitab software. The experimental results showed different combinations of HA- and GO-enhanced mentioned mechanical properties in various states. In the second step, a statistical modeling has been done by response surface method (RSM), artificial neural network (ANN) and decision tree methods. Modeling results showed that ANN and decision tree methods have the best fitness. Finally, the mechanical properties are optimized by genetic algorithm. The optimum values are 21.54 MPa for flexural strength in 5.17 wt% HA and 0.38 wt% Go and 25.7 GPa for flexural modulus in 2.73 wt% HA and 0.195 wt% GO. Also, the optimum results for compression strength are 23.95 MPa in 7 wt% HA and 0.289 wt% GO, and also 690.5 MPa for compression modulus in 6.89 wt% HA and 0.007 wt% GO. Effective mechanisms of fillers have been analyzed by SEM and observed that debonding, crack path deflection, plastic void growth and pullout were dominant.

Electrophoretic deposition of chitosan reinforced graphene oxide-hydroxyapatite on the anodized titanium to improve biological and electrochemical characteristics

Chitosan reinforced hydroxyapatite-graphene oxide (CS-GO-HA) nanocomposite coatings were developed using electrophoretic deposition process in order to improve the biological and electrochemical properties of Ti surface. Moreover, the role of anodized layer on the physical and electrochemical properties of the CS-GO-HA nanocomposite coating was evaluated. After synthesize of HA-GO nanopowder using a sol-gel process, nanocomposite coatings with various concentrations of chitosan (0.5, 1 and 1.5 mg/ml) were produced. Increasing the chitosan content lowered the deposition rate of HA-GO nanoparticles, reduced the coating thickness and diminished apatite-formation ability and biocompatibility. Noticeably, MG63 cell viability significantly reduced form 119.3 ± 5.1 (% control) to 51.9 ± 14.8 (% control), when the chitosan concentration increased from 0.5 to 1.5 mg/ml. In addition, the CS-GO-HA coating containing 0.5 mg/ml chitosan revealed the best barrier property owing to the less crack formation. Furthermore, anodizing of titanium substrate and formation of TiO2 nanotube (TiNT) resulted in the formation of crack-free and homogeneous CS-GO-HA coatings without any observable defect. Moreover, the TiNT formation noticeably improved barrier resistance of the coating (6.7 times) due to better adhesion governed between coating and substrate. Our results confirmed that the surface modification using both anodizing of Ti substrate and electrophoretic deposition of ternary CS-GO-HA nanocomposite coating with 0.5 mg/ml chitosan successfully improves electrochemical properties, bioactivity and cell function, which makes it promising for bone implant applications.

Adsorption of Extracellular Matrix Protein Fibronectin on the Surface of the Nanocomposite Particle of Graphene Oxide-Hydroxyapatite

Adsorption of Extracellular Matrix Protein Fibronectin on the Surface of the Nanocomposite Particle of Graphene Oxide-Hydroxyapatite